Photonic systems for tunable mm-wave and THz wireless communications

In this paper we present two different techniques for photonic generation of millimeter and THz waves. Each of them tackles the phase noise problem associated with optical sources in a different way. The first one relays on the heterodyne down-conversion of two phase noise correlated optical tones. The correlation is achieved by generation of an optical frequency comb. To select one of the optical lines we use an optical phase lock loop, which besides enabling a frequency offset between output and input, can provide optical gain and is highly selective. The second one relays on the envelope detection of a single sideband-with carrier signal. In this approach the photonic remote antenna unit is implemented as monolithically integrated photonic chip

Generation of continuous wave terahertz frequency radiation from metal-organic chemical vapour deposition grown Fe-doped InGaAs and InGaAsP

We demonstrate the generation of continuous wave terahertz (THz) frequency radiation from photomixers fabricated on both Fe-doped InGaAs and Fe-doped InGaAsP, grown by metal-organic chemical vapor deposition. The photomixers were excited using a pair of distributed Bragg reflector lasers with emission around 1550 nm, and THz radiation was emitted over a bandwidth of greater than 2.4 THz. Two InGaAs and four InGaAsP wafers with different Fe doping concentrations were investigated, with the InGaAsmaterial found to outperform the InGaAsP in terms of emitted THz power. The dependencies of the emitted power on the photomixer applied bias, incident laser power, and materialdoping level were also studied

Ultra-high-resolution software-defined photonic terahertz spectroscopy

A novel technique for high-resolution 1.5 µm photonics-enabled terahertz (THz) spectroscopy using software control of the illumination spectral line shape (SLS) is presented. The technique enhances the performance of a continuous-wave THz spectrometer to reveal previously inaccessible details of closely spaced spectral peaks. We demonstrate the technique by performing spectroscopy on LiYF4:Ho3+, a material of interest for quantum science and technology, where we discriminate between inhomogeneous Gaussian and homogeneous Lorentzian contributions to absorption lines near 0.2 THz. Ultra-high-resolution ( 2 × 109 is achieved using an exact frequency spacing comb source in the optical communications band, with a custom uni-traveling-carrier photodiode mixer and coherent down-conversion detection. Software-defined time-domain modulation of one of the comb lines is demonstrated and used to resolve the sample SLS and to obtain a magnetic field-free readout of the electronuclear spectrum for the Ho3+ ions in LiYF4:Ho3+. In particular, homogeneous and inhomogeneous contributions to the spectrum are readily separated. The experiment reveals previously unmeasured information regarding the hyperfine structure of the first excited state in the 5 I8 manifold complementing the results reported in Phys. Rev. B 94, 205132 (2016).ISSN:2334-253

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Supplementary text and figure